
package com.ulwx.tool.path;

import com.ulwx.tool.Assert;

import java.io.*;
import java.net.URI;
import java.net.URL;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.nio.file.FileSystem;
import java.nio.file.*;


class FileSystemResource extends AbstractResource implements WritableResource {

   private final String path;

   private final File file;

   private final Path filePath;


   /**
    * Create a new {@code FileSystemResource} from a file path.
    * <p>Note: When building relative resources via {@link #createRelative},
    * it makes a difference whether the specified resource base path here
    * ends with a slash or not. In the case of "C:/dir1/", relative paths
    * will be built underneath that root: e.g. relative path "dir2" ->
    * "C:/dir1/dir2". In the case of "C:/dir1", relative paths will apply
    * at the same directory level: relative path "dir2" -> "C:/dir2".
    * @param path a file path
    * @see #FileSystemResource(Path)
    */
   public FileSystemResource(String path) {
       Assert.notNull(path, "Path must not be null");
       this.path = PStringUtils.cleanPath(path);
       this.file = new File(path);
       this.filePath = this.file.toPath();
   }

   /**
    * Create a new {@code FileSystemResource} from a {@link File} handle.
    * <p>Note: When building relative resources via {@link #createRelative},
    * the relative path will apply <i>at the same directory level</i>:
    * e.g. new File("C:/dir1"), relative path "dir2" -> "C:/dir2"!
    * If you prefer to have relative paths built underneath the given root directory,
    * use the {@link #FileSystemResource(String) constructor with a file path}
    * to append a trailing slash to the root path: "C:/dir1/", which indicates
    * this directory as root for all relative paths.
    * @param file a File handle
    * @see #FileSystemResource(Path)
    * @see #getFile()
    */
   public FileSystemResource(File file) {
       Assert.notNull(file, "File must not be null");
       this.path = PStringUtils.cleanPath(file.getPath());
       this.file = file;
       this.filePath = file.toPath();
   }

   public FileSystemResource(Path filePath) {
       Assert.notNull(filePath, "Path must not be null");
       this.path = PStringUtils.cleanPath(filePath.toString());
       this.file = null;
       this.filePath = filePath;
   }

   /**
    * Create a new {@code FileSystemResource} from a {@link FileSystem} handle,
    * locating the specified path.
    * <p>This is an alternative to {@link #FileSystemResource(String)},
    * performing all file system interactions via NIO.2 instead of {@link File}.
    * @param fileSystem the FileSystem to locate the path within
    * @param path a file path
    * @since 5.1.1
    * @see #FileSystemResource(File)
    */
   public FileSystemResource(FileSystem fileSystem, String path) {
       Assert.notNull(fileSystem, "FileSystem must not be null");
       Assert.notNull(path, "Path must not be null");
       this.path = PStringUtils.cleanPath(path);
       this.file = null;
       this.filePath = fileSystem.getPath(this.path).normalize();
   }


   /**
    * Return the file path for this resource.
    */
   public final String getPath() {
       return this.path;
   }

   /**
    * This implementation returns whether the underlying file exists.
    * @see File#exists()
    */
   @Override
   public boolean exists() {
       return (this.file != null ? this.file.exists() : Files.exists(this.filePath));
   }

   /**
    * This implementation checks whether the underlying file is marked as readable
    * (and corresponds to an actual file with content, not to a directory).
    * @see File#canRead()
    * @see File#isDirectory()
    */
   @Override
   public boolean isReadable() {
       return (this.file != null ? this.file.canRead() && !this.file.isDirectory() :
               Files.isReadable(this.filePath) && !Files.isDirectory(this.filePath));
   }

   /**
    * This implementation opens a NIO file stream for the underlying file.
    * @see java.io.FileInputStream
    */
   @Override
   public InputStream getInputStream() throws IOException {
       try {
           return Files.newInputStream(this.filePath);
       }
       catch (NoSuchFileException ex) {
           throw new FileNotFoundException(ex.getMessage());
       }
   }

   /**
    * This implementation checks whether the underlying file is marked as writable
    * (and corresponds to an actual file with content, not to a directory).
    * @see File#canWrite()
    * @see File#isDirectory()
    */
   @Override
   public boolean isWritable() {
       return (this.file != null ? this.file.canWrite() && !this.file.isDirectory() :
               Files.isWritable(this.filePath) && !Files.isDirectory(this.filePath));
   }

   /**
    * This implementation opens a FileOutputStream for the underlying file.
    * @see java.io.FileOutputStream
    */
   @Override
   public OutputStream getOutputStream() throws IOException {
       return Files.newOutputStream(this.filePath);
   }

   /**
    * This implementation returns a URL for the underlying file.
    * @see File#toURI()
    */
   @Override
   public URL getURL() throws IOException {
       return (this.file != null ? this.file.toURI().toURL() : this.filePath.toUri().toURL());
   }

   /**
    * This implementation returns a URI for the underlying file.
    * @see File#toURI()
    */
   @Override
   public URI getURI() throws IOException {
       return (this.file != null ? this.file.toURI() : this.filePath.toUri());
   }

   /**
    * This implementation always indicates a file.
    */
   @Override
   public boolean isFile() {
       return true;
   }

   /**
    * This implementation returns the underlying File reference.
    */
   @Override
   public File getFile() {
       return (this.file != null ? this.file : this.filePath.toFile());
   }

   /**
    * This implementation opens a FileChannel for the underlying file.
    * @see FileChannel
    */
   @Override
   public ReadableByteChannel readableChannel() throws IOException {
       try {
           return FileChannel.open(this.filePath, StandardOpenOption.READ);
       }
       catch (NoSuchFileException ex) {
           throw new FileNotFoundException(ex.getMessage());
       }
   }

   /**
    * This implementation opens a FileChannel for the underlying file.
    * @see FileChannel
    */
   @Override
   public WritableByteChannel writableChannel() throws IOException {
       return FileChannel.open(this.filePath, StandardOpenOption.WRITE);
   }

   /**
    * This implementation returns the underlying File/Path length.
    */
   @Override
   public long contentLength() throws IOException {
       if (this.file != null) {
           long length = this.file.length();
           if (length == 0L && !this.file.exists()) {
               throw new FileNotFoundException(getDescription() +
                       " cannot be resolved in the file system for checking its content length");
           }
           return length;
       }
       else {
           try {
               return Files.size(this.filePath);
           }
           catch (NoSuchFileException ex) {
               throw new FileNotFoundException(ex.getMessage());
           }
       }
   }

   /**
    * This implementation returns the underlying File/Path last-modified time.
    */
   @Override
   public long lastModified() throws IOException {
       if (this.file != null) {
           return super.lastModified();
       }
       else {
           try {
               return Files.getLastModifiedTime(this.filePath).toMillis();
           }
           catch (NoSuchFileException ex) {
               throw new FileNotFoundException(ex.getMessage());
           }
       }
   }


   @Override
   public Resource createRelative(String relativePath) {
       String pathToUse = PStringUtils.applyRelativePath(this.path, relativePath);
       return (this.file != null ? new FileSystemResource(pathToUse) :
               new FileSystemResource(this.filePath.getFileSystem(), pathToUse));
   }

   /**
    * This implementation returns the name of the file.
    * @see File#getName()
    */
   @Override
   public String getFilename() {
       return (this.file != null ? this.file.getName() : this.filePath.getFileName().toString());
   }

   /**
    * This implementation returns a description that includes the absolute
    * path of the file.
    * @see File#getAbsolutePath()
    */
   @Override
   public String getDescription() {
       return "file [" + (this.file != null ? this.file.getAbsolutePath() : this.filePath.toAbsolutePath()) + "]";
   }


   /**
    * This implementation compares the underlying File references.
    */
   @Override
   public boolean equals( Object other) {
       return (this == other || (other instanceof FileSystemResource &&
               this.path.equals(((FileSystemResource) other).path)));
   }

   /**
    * This implementation returns the hash code of the underlying File reference.
    */
   @Override
   public int hashCode() {
       return this.path.hashCode();
   }

}
